Plastic bottles and similar containers having internal spiders

ABSTRACT

A blow-molded plastics bottle having a neck, a side wall and a base, includes an internal spider attached to the side wall of the bottle. The spider and the side wall are formed from biaxially-oriented plastics such that the strength of the bottle is increased and such that the bottle resists the pressures caused by the contents thereof.

BACKGROUND OF THE INVENTION

This invention relates to plastics bottles and similar containers andparticularly those intended to contain their contents under pressure.Traditionally returnable glass bottles have been used to containpressurised beverages and other liquids. It is common for suchreturnable glass bottles to make up a proportion as high as 90% of thetotal load to be transported. By using non-returnable glass bottles theweight of the bottles can be reduced to about 55% of the total load butby using modern plastics materials such as blow moulded PET it ispossible to reduce the weight of the containers to a level as low asabout 11% of the total load. This leads to considerable reductions intransport and distribution costs.

Large bottles even when not containing carbonated, or other pressurisedbeverages must still have side walls of considerable strength to containthe weight of their contents. When bottles and similar containers haveto resist pressurised contents such as carbonated beverages they have towithstand considerable internal pressures. As an example of this a beercontaining 2.5 volumes of carbon dioxide exerts a pressure on the sidewall of the container of approximately 11/2 bar at for example 60° F.(16° C.) and this can increase to a pressure as high as 3 bar at 90° F.(32° C.). The ideal shape of a container to resist such internalpressures is for them to be substantially spherical. However, this shapeis not preferred for packaging purposes and so, conventionally, theshape is rationalised by the bottles or similar containers having agenerally cylindrical shape with domed ends. By forming plastics bottlesor similar containers in this way they are shaped to resist the loadexerted by the contents whether this results from the mere weight of thecontents or whether this results from the pressurised nature of thecontents.

Blow moulded plastics bottles are also known which include an internaldivision which divides the bottle into separate compartments. Examplesof such bottles are described in U.S. Pat. No. A-4,070,140, U.S. Pat.No. -4,217,328 and FR-A-1,258,792.

FR-A-1,258,792 describes a blow moulded plastics bottle having a neckformed to receive a bottle closure, a side wall and a base, andincluding an internal spider attached to the side wall and extendingacross the inside of the bottle.

SUMMARY OF THE INVENTION

According to this invention such a bottle or similar container ischaracterised in that the material in the side wall and spider, atleast, of the bottle or other container is bi-axially oriented so thatthe spider resists tension and acts as an internal reinforcingstructure.

The plastics bottle or similar container is preferably formed byinitially injection moulding a preform and then blowing the injectionmoulded preform into a mould cavity thereby bi-axially orienting theside wall and spider, at least, of the bottle.

Usually the bottle or similar container is formed by a stretch-blowmoulding technique in which the injection moulded preform is firststretched axially into substantially its final axial length before beingblown to its final transverse dimension. This axial stretching may takeplace by the top of the axial preform which is to form the neck of thebottle being held in a mould and, at the same time, the base of thepreform being pushed away from the neck by more than one push rod whichenters the preform through the neck and engages its base to push it awayfrom the neck to stretch axially the preform. There may be half as manypush rods as there are compartments formed within the bottle by thespider but preferably there are an equal number of push rods and dividedcompartments inside the bottle. Thus, where the spider is cruciform incross section four separate push rods are preferably included whichengage the base of the preform in each compartment.

Another way of axially stretching the preform is, whilst the neck of thepreform is being held in a mould, to engage the outside of the base ofthe preform and pull this downwards away from the neck. One way ofachieving this is to provide a suction cup which fits over the base ofthe preform and then move the suction cup away from the neck moulding tostretch axially the preform. Alternatively, the preform may be formedwith an external tab and, in this case, a gripper is provided to gripthe external tab and axially stretch the preform whilst its neck isheld.

A further way in which the preform can be axially stretched is for themould in which the neck of the preform or parison is formed to have alength substantially equal to the final axial length of the preform butto have a width which is considerably less than the final width of thebottle. Then, the preform or parison is subjected to an initial blowingstep in which it is blown into this first, narrow mould, during whichthe preform is axially stretched to substantially its final length.Subsequently, the preform is demoulded and placed into its final mouldwhere it is blown to its final width.

Preferably the preform is blow moulded immediately after it is injectionmoulded and whilst it is still hot. Typically the hot preform issubjected to an initial thermal conditioning step before blowing whichensures that the entire preform is at a constant, elevated temperaturetypically in a range of 85° to 100° C. Preferably, as part of thisthermal conditioning step more than one thermal conditioning rod isinserted through the neck into the inside of the preform. Again theremay be half the number of thermal conditioning rods as there are dividedcompartments inside the preform and bottle or similar container butpreferably there is an equal number of thermal conditioning rods asthere are divided compartments inside the preform and bottle or similarcontainer. The thermal conditioning rods are each formed as the thermalconditioning rods used in conventional blow moulding equipment and thustypically formed as heat pipes.

The internal spider may extend substantially the whole length of thebottle or similar container from its neck to its base and, in this case,is preferably absent from the neck of the bottle or similar container toenable the bottle or similar container to be filled by conventionalfilling machinery. Alternatively the internal spider only extends overpart of the length of the bottle or other container. Thus the spider mayonly be present towards the base of the bottle when it is used tobuttress and support the base of the bottle or similar container.Instead the spider may be present only towards the top of the bottle orsimilar container when it is only necessary to buttress this region ofit. When the spider only extends over part of the length of the bottleor similar container communication between the various chambers formedinside the bottle or similar container is improved.

The neck of the bottle or similar container may be formed to receive are-closeable bottle closure such as, for example, a screw cap or twistoff closure or alternatively the neck of the bottle or similar containermay be formed to receive a one-use-only bottle closure such as a crowncap or ring pull type of closure. The one-use-only type of closure mayalso be formed by a tear strip which is heat or adhesively sealed to theneck of the bottle or similar container. Typically the form of thebottle closure is conventional in construction to enable the bottles orsimilar containers to be used with conventional filling and cappingmachinery.

The internal spider preferably has the form of planar webs extendinggenerally radially across the inside of the bottle and joining togetherat the central longitudinal axis of the bottle or similar container. Inthis case the spider typically has three, four, six or eightequiangularly spaced radial webs. Another form for the spider is for itto have a central substantially planar web which divides into two ormore webs before being joined to the side walls of the bottle or similarcontainer. Thus, in cross section the spider has the form of twoback-to-back Y's.

Preferably the thicknesses of the elements (i.e., the webs) of thespider are tapered, and are greatest adjacent the longitudinal axis ofthe bottle or similar container. The elements of the spider may also bethinnest at a central region of each element and increase in thicknessagain before they meet and join the side wall of the bottle or similarcontainer. This configuration which is encouraged by shaping of thepreform provides a controlled expansion of the bottle during blowing anda controlled bi-axial orientation of the material in the elements of thespider.

The bottle or similar container may be formed of PET (polyethyleneterephthalate, polypropylene, OPVC (oriented polyvinylchloride),polycarbonate, nylon or multilayers including PET, nylon, andethylene-vinyl alcohol co-polymer. The choice of material for the bottleor similar container is largely governed by the contents of it. Wherethese are sensitive to the ingress of oxygen it is naturally importantto select materials which have a low oxygen permeability and, for this,multilayers are preferred.

The internal spider formed inside bottles and other containers inaccordance with this invention is bi-axially oriented and so provides amember which resists tension and so resists outward deformation of theside wall. This firstly reinforces the bottles or similar containers andso helps them to resist an internal pressure resulting from either theweight of the contents or the pressurised nature of the contents.Secondly, and perhaps more importantly it enables plastics bottles andsimilar containers to be formed with shapes other than cylindrical withdomed ends and yet still to have sufficient strength to resist theinternal pressures generated by the filling. Where the internal spiderextends down to and is connected to the base of the bottle or similarcontainers this can be made substantially flat or slightly concave andyet still resist an internal pressure resulting from its pressurisedcontents. By making a bottle or similar container in this form it isstable. The internal spider buttresses the side wall of the bottle andso enables the bottle or similar container to be, for example, polygonalin shape, in this case, preferably the spider is connected to the middleof panels in the side wall of the bottle or similar container or to eachlongitudinally extending corner of the bottle or similar container. Inthis way it is possible to have bottles and similar containers with asubstantially square cross-section and bottles and similar containerswhich are substantially rectangular in form and so which provide themaximum possible packing density for transport or subsequent storageeither by a distributor or by the end user. Such a bottle shapeincreases the volume efficiency during transport and storage by over20%. Alternatively the side wall may have a re-entrant form.

BRIEF DESCRIPTION OF THE DRAWINGS

Particular examples of plastics bottles and similar containers inaccordance with this invention will now be described with reference tothe accompanying drawings, in which:

FIG. 1 is a diagram illustrating a method of making a bottle;

FIG. 2 is a side elevation of a preform;

FIG. 3 is a cross-section through the preform;

FIG. 4 is a side elevation of a first example of a finished bottle;

FIG. 5 is a plan of the first example of a finished bottle;

FIG. 6 is a cross-section through the first example of a finishedbottle;

FIGS. 7A and B are a side elevation and cross-section, respectively,through a second example;

FIGS. 8A and B are a side elevation and cross-section, respectively,through a third example;

FIG. 9 is a longitudinal section through a fourth example;

FIG. 10 is a partially cut-away perspective view of a fifth example;

FIG. 11 is a cross-section through a sixth example;

FIG. 12 is a cross-section through a quadrant of the sixth example drawnto a larger scale;

FIG. 13 is a cross-section through a modification of the sixth example;

FIG. 14 is a longitudinal section through the sixth example;

FIGS. 15 and 16 are radial sections showing alternative side profilesfor the top of the sixth example; and,

FIGS. 17, 18 and 19 are a cross-sections through three further examplesof blow moulded bottles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An injection moulded preform 1 shown in FIGS. 2 and 3 is injectionmoulded in an entirely conventional injection moulding machine 2. Thepreform 1 comprises a neck 3 with a moulded male screw thread 4 arrangedto receive a screw-on closure (not shown), and a body forming portion 5.An internal spider 6 having a cruciform cross-section is located insidethe body forming portion 5. As soon as the preform 1 has cooledsufficiently to be self supporting it is transferred to a conditioningstation 7. The conditioning station 7 comprises an outer heatedconditioning pot 8 and four conditioning rods 9 consisting of heat pipeswhich enter through the neck 3 of the injection moulded preform 1 intointernal cavities formed between the elements of the cruciform spider 6and side wall 5 of the preform. The preform 1 is held at theconditioning station 7 until it has a completely uniform temperature oftypically 90° C. When the plastics material is injection moulded ittypically has a temperature of the order of hundreds of ° C. and thus,at the conditioning station 7 the preform is cooled until it is all at aconstant elevated temperature. The preform is then moved to an axialstretching station 17 in which four stretch rods 18 enter through theneck 3 of the preform 1 and move downwards axially to stretch thepreform 1 until it has a length corresponding to that of the finishedbottle. At the completion of the axial stretching of the preform 1 thestretch rods 18 are removed and then the axially stretched preform ismoved to a blowing station 28 in which it is blown into a mould toprovide a bottle of required shape.

The first example of a bottle is generally rectangular in shape andsquare in cross-section and is shown in FIGS. 4, 5 and 6. It comprises abottle 10 with a body portion 11, neck 12 of circular cross-section, andbase 13. A side wall of the body of the bottle consists of flat panels14 connected by chamfered corner portions 15. A cruciform spider 16 isjoined to the middle of each flat panel 14. The wall thickness of theside wall in the panels 14 decreases away from their junctions with thespider 16 with the chamfered regions 15 having the smallest thickness.The wall thickness of the blades of the spider 16 is narrowest in thecentre of each blade and greatest at the joint with the panels 14 andalong the central longitudinal axis of the bottle 10.

During the stretch and blow moulding performed on the preform 1 thematerial forming the side wall of the bottle 5, the spider 6, and tosome extent its base, is bi-axially oriented so, thereby increasingtensile strength considerably and reducing its permeability. Thus thematerial in the side wall 11, spider 16 and to some extent the base 13,is bi-axially oriented. In this example the preform 1 is injectionmoulded from PET to provide a clear transparent bottle.

The remaining examples of bottles are all manufactured by a similartechnique.

The second example of a bottle shown in FIG. 7 is generally square incross-section and comprises a bottle 20 with a neck 22 of circularcross-section, a side wall 23 which in the body of the bottle issubstantially square in cross-section and a base 24. An internalcruciform sectioned spider 26 extends across the diagonals of the bottle20.

A third example of a bottle is shown in FIG. 8 and comprises a bottle 30with a cylindrical neck 32 which leads via a re-entrant portion 35 to ahexagonal body 33 above base 34. A six bladed internal spider 36 extendsto the vertices of the hexagonal body 33 and is formed inside the bottle30.

The fourth example 40 shown in FIG. 9 again has a substantially squarebody portion 41 and a generally cylindrical neck 42. An internal spider46 is included which is cruciform in section and absent from the top ofthe cylindrical neck region 42 and from adjacent a base 44 of thebottle. The cylindrical neck portion 42 is formed to receive aconventional screw top 47.

A fifth example which is somewhat similar to the second example is shownin FIG. 10 which is cut away to illustrate the internal structure of thebottle 50 to show a spider 56 and a screw cap 57.

A sixth example of bottle 60 in accordance with this invention is shownin FIG. 11 to 14. The bottle 60 has a generally cylindrical body portion61 and neck 62 with a re-entrant portion 63 joining the body 61 to theneck 62. The bottle 60 includes an internal spider 66 which is absentfrom the top of the neck as shown in FIG. 14 and which has a three orfour blades as shown in FIGS. 11 and 13. FIGS. 15 and 16 showalternative forms for the re-entrant portion 63 joining the body 61 tothe neck 62. The portion of the neck 62 to receive a bottle closure hasbeen omitted from FIGS. 14, 15 and 16 for clarity.

FIG. 12 illustrates the thickness profile of a quadrant of the bottle 60illustrating that the thickness of the webs forming the internal spider66 decreases from their centre to their outside and that, theirthickness adjacent their centre is typically four times the side wallthickness of the bottle whilst their thickness towards the side wall isapproximately 2.6 times the side wall thickness.

FIGS. 17, 18 and 19 show alternate forms for blown bottles in accordancewith the sixth example of this invention and illustrate in FIG. 17 howthe side wall 61 typically bows out over the regions where it is notconnected to the internal spider 66. This effect can be exaggerated byintroducing profiling into the side wall to produce blown bottles whichare substantially square in cross-section as shown in FIG. 18 or can beused to provide a decorative feature and provide a vertically flutedbottle as shown in FIG. 19 by using an eight bladed spider 66.

I claim:
 1. A blow moulded plastics bottle (10) having a neck (12)formed to receive a bottle closure, a side wall (11) and a base (13),and including an internal spider (16) attached to the side wall (11),said spider extending approximately from the neck to the base and acrossthe inside of the bottle (10), characterised in that the material in theside wall (11) and the spider (16) is bi-axially oriented so that thespider (16) resists tension and acts as an internal reinforcingstructure to prevent outward deformation of the side walls.
 2. Aplastics bottle according to claim 1, prepared by a process comprisingthe steps of:injection molding a preform; and blowing the injectionmoulded preform into a mould cavity thereby bi-axially orienting atleast the side wall (11) and the spider (16) of the bottle (10).
 3. Aplastics bottle according to claim 2, in which the bottle is furtherprepared by a stretch-blow moulding technique comprising axiallystretching the injection moulded preform into substantially its finalaxial length before the preform is blown to its final transversedimension.
 4. A plastics bottle according to any one of claim 1 to 3, inwhich the internal spider (16) extends substantially the whole length ofthe bottle (10) from its neck (12) to its base (13) and, in which thespider (16) is absent from the neck (12).
 5. A plastics bottle accordingto any one of claims 1 to 3, in which the internal spider (16) onlyextends over part of the length of the bottle (10).
 6. A plastics bottleaccording to any one of claims 1 to 3, in which the internal spider (16)has the form of planar webs extending generally radially across theinside of the bottle (10) and joining together at the centrallongitudinal axis of the bottle (10).
 7. A plastics bottle according toany one of claims 1 to 3, in which the thicknesses of elements of thespider are tapered and are greatest adjacent the longitudinal axis ofthe bottle.
 8. A plastics bottle according to any one of claims 1 to 3,formed of a plastic selected from the group consisting of PET(polyethylene terephthalate), polypropylene, OPVC (orientedpolyvinylchloride), polycarbonate, nylon, and multilayers including PET,nylon, and ethylene-vinyl alcohol co-polymer.